1. Field of the Invention
The invention is in the field of medical technology. In particular, it relates to medical devices, medical apparatus and medical methods, especially to implants, apparatuses for implantation, and implantation methods.
2. Description of Related Art
If screws are anchored in live bone tissue, often the problem of insufficient bone stability or insufficient stability of the anchoring in the bone arises. Especially, in trabecular bone tissue, any load acting on the screw is passed over to only few trabeculae, with adverse consequences both for the load bearing capability of the screw-bone connection and for its long-time stability. This is especially severe in osteoporotic or osteopenic or otherwise weakened bone tissue.
One solution of this problem is the use of an alternative anchoring method that is suitable also for tissue in which screws are not stable. The publications WO 02/069817, WO 2004/017 857, WO 2008/034 277, and WO 2009/055 952 concern anchorage of an implant in bone tissue with the aid of mechanical vibration and a thermoplastic material which is liquefiable by the mechanical vibration, i.e. the thermoplastic material is capable of being liquefied when vibrated and simultaneously kept in contact with a non-vibrating surface. The thermoplastic material, where in contact with the bone tissue, is liquefied and pressed into pores or cavities of the bone tissue to constitute, when re-solidified, a positive fit connection with the bone tissue.
A special group of embodiments of implants and implant anchoring processes is based on the liquefiable material being inserted (pre-assembled or inserted in situ) in a longitudinal bore of a sheath element. The sheath element comprises at least one hole in the sheath element wall, through which the liquefied material is pressed from the longitudinal bore into the structures (pores or cavities or other structures) of the bone tissue or other hard tissue or hard tissue replacement material in which anchoring is desired. This principle of pressing liquefied material out of a tube or sleeve element with lateral openings is for example described in U.S. Pat. No. 7,335,205, U.S. Pat. No. 6,921,264, WO 2009/055 952, WO 2009/010247, WO 2009/010234, and PCT application No. PCT/CH 2009/000138, all of which are incorporated herein by reference.